Answer :
The nation currently not experiencing widespread measles cases or epidemics is B. United States.
In determining which nation is not currently experiencing widespread measles cases or epidemics, we need to assess recent data on measles outbreaks. According to the World Health Organization (WHO), as of the latest available data, the United States has successfully maintained relatively high vaccination coverage rates, contributing to the prevention of widespread measles outbreaks. This is evidenced by the CDC's surveillance data, which indicates sporadic cases but no large-scale epidemics in recent years.
Furthermore, the United States has robust public health infrastructure and vaccination programs in place, which have been effective in controlling the spread of measles. Vaccination coverage, including the MMR (measles, mumps, and rubella) vaccine, remains high, reducing the risk of outbreaks. Additionally, the country's healthcare system enables swift responses to any isolated cases, preventing them from escalating into larger outbreaks.
In contrast, other options such as the Democratic Republic of Congo, Venezuela, Syria, and the Philippines have faced challenges in controlling measles due to factors like limited healthcare infrastructure, political instability, and vaccine hesitancy. Therefore, based on current data and public health measures, the correct option is B. United States.